With the development of network communication technologies, various access authentication methods have been adopted for communication networks. Portal authentication is becoming increasingly popular for network operators because of its power supporting capability for new services, elimination of the need for client software, and the like. During implementation of a Portal authentication, to charge a user accurately for its access to the network, it is necessary to monitor the online state of the user in real time. More specifically, when a user logs in successfully, the client terminal sends handshaking packets to the Portal Server periodically. If the Portal Server does not receive the handshaking packets after a given period of time, the Portal Server will force the user to log off to prevent the accounting server from charging the user when the user cannot communicate with the Portal Server.
Currently, the handshaking mechanism referenced above can be implemented as follows. When a user logs in successfully, an application or a control unit is downloaded for the user. The downloaded application periodically creates a TCP/IP connection with the Portal Server, sends handshaking request packets to the Portal Server, and then waits for the response packets from the Portal Server. After receiving a handshaking request packet from the user, the Portal Server updates the on-line time of the user and sends a response packet to the user terminal. After receiving a response packet from the Portal server side, the application or control unit on the user terminal side carries out the proper operations based on the returned connection state of the user. If the Portal Server has not received the user's handshaking request packet after a given period of time, the user will be deemed as being off-line and the Portal Server will send a stop charging packet to the device side.
Such a handshaking mechanism requires installation of an application on the user terminal to ensure the accuracy of charges for a user's access to the network. With ongoing developments in computer technology, software packages for use with a computer are also constantly updated. Therefore, implementation methods such as those described above based on the handshaking mechanism of the Portal authentication can have limitations in application. For example, when the browser on the user terminal is set to a higher security level, the software for sending handshaking request packets often cannot be downloaded. Even if the software is downloaded, the downloaded software often cannot run because of a different operating environment such as different operating systems of the users. In such cases, the handshaking mechanism based on Portal authentication cannot be implemented. The user's online state cannot be monitored and the user who accesses the network can not be charged accurately, which is unacceptable not only to the users but also to the network operators.